Various techniques have been developed for producing micro-mechanical devices from semiconductor wafers. These techniques make use of equipment and methods that have been developed for microelectronics manufacturing, such as thin-film deposition and photolithography, in order to create moving mechanical devices on micrometer scales.
For example, U.S. Pat. No. 7,952,781, whose disclosure is incorporated herein by reference, describes a method of scanning a light beam and a method of manufacturing a microelectromechanical system (MEMS), which can be incorporated in a scanning device. The disclosed method of manufacturing uses a silicon-on-insulator (SOI) wafer, which typically comprises a silicon layer on its front side, another silicon layer on its back side, and a thin “stop” layer therebetween. The steps of the method include thinning of the silicon, deposition of silicon dioxide (SiO2), lithography, etching, and metal deposition. Two etching processes are employed: reactive ion etching (RIE) and dry reactive ion etching (DRIE, also known as deep reactive ion etching) to expose the “stop” layer. The substrate then is separated into chips and subjected to a cleaning process, whereupon a rotatable micromirror is formed.